Hot balloon catheters are known in the art for PTCA treatment wherein cardiac catheterization is carried out by directing an inflatable balloon in a coronary artery in the region of a coronary narrowing, and U.S. patents disclosing such treatment are J. R. Spears Pat. Nos. 4,512,762; 4,773,899; 4,799,479; 5,019,075 and 5,092,841; and Sinofsky et al. 4,878,492.